The San Diego County Water Authority is expecting to save approximately $100,000 per year with commercial-scale batteries installed at the agency’s solar-powered Twin Oaks Valley Water Treatment Plant near San Marcos. The energy storage system is designed to reduce operational costs at the facility by storing low-cost energy for use during high-demand periods when energy prices increase. The batteries were installed at no charge to the agency as part of an agreement with Santa Clara-based ENGIE Storage, formerly known as Green Charge.